Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 43 for “"waveform inversion"”.
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Born Waveform Inversion in Shot Coordinate Domain
The goal of this thesis is to integrate Born waveform inversion, variable projection algorithm and model extension concept to get a method that can improve the long scale background model updates reliably and efficiently from seismic data. Born waveform inversion is a partially linearized version …
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Direct Waveform Inversion Using Explicit Time-Space Causality Principle
I have developed a Direct Waveform Inversion (DWI) scheme to simultaneously address several existing challenges in full waveform inversion (FWI). A key ingredient in the DWI is the explicit use of the wavefield time-space causality property in the inversion, which allows us to convert the global …
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Modeling, imaging and waveform-inversion in attenuative anisotropic media
… and imaging. In this thesis, I develop a waveform-inversion (WI) methodology for attenuation estimation, as well as an attenuation- compensated time-reversal (TR) imaging algorithm, for transversely isotropic media with a vertical symmetry axis (VTI). The attenuation model is assumed to …
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Efficient Tunnel Detection with Waveform Inversion of Back-scattered Surface Waves
… velocity anomaly detection method by using waveform inversion of the back-scattered surface waves (BSWI) is proposed. The main objective of this thesis is to review the theoretical background and study the feasibility of the proposed BSWI method. The proposed BSWI method is tested with …
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Structure of the earth’s topmost inner core from seismic waveform inversion
… inner core, I have developed an automatic waveform inversion technique based on Neighborhood Algorithm. This method takes advantage of the triplicated PKP waveforms at epicentral distances from 130 to 142 degrees and allows us to model P-wave velocity and attenuation structure of the inner …
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Efficient modeling and waveform inversion of multicomponent seismic data for anisotropic media
… wavefields is crucial for seismic imaging and inversion applications. Incorrect handling of the boundary conditions can distort the wavefield solutions, especially the horizontal displacement and velocity components, which may have serious implications for elastic reverse time migration (ERTM) …
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Full waveform inversion combining rock physics for seismic reservoir characterization and monitoring
… on amplitude variation with offset (AVO). Full waveform inversion (FWI) methods, although computationally more complex than AVO approaches, can produce more accurate elastic models by extracting the full information content in the seismogram. Progress has been reported in using elastic FWI …
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Seismic imaging with traveltime and waveform inversion: Naga Thrust and Fold Belt, India
I demonstrate the utility of traveltime and waveform inversion in depth imaging of seismic data with the help of two 2-D multichannel seismic lines, Reg-07 and PO-03, shot perpendicular to the trend of the Naga Thrust and Fold Belt (NTFB), India. I use both lines to demonstrate that a) a velocity …
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Machine learning methods modeling waveform, multi-parameter full waveform inversion, and uncertainty quantification
Full waveform inversion (FWI) is a potent technology capable of estimating subsurface parameters using seismic records. However, several challenges hinder its widespread application in large-scale field operations. In this thesis, I introduce strategies that leverage machine learning techniques to …
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Distributed acoustic sensing: modelling, full waveform inversion, and its use in seismic monitoring
… modes that are crucial to support land full waveform inversion (FWI). The inherently different sampling that DAS fibers provide leads to a requirement for modeling strategies that differ from those used to simulate point sensor data. To maximize the potential of DAS which only samples …
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Focal depths and mechanisms of mid-ocean ridge earthquakes from body waveform inversion
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1986.
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Full-waveform inversion of time-lapse seismic data using physics-based and data-driven techniques
Time-lapse (4D) full-waveform inversion (FWI) is an advanced seismic technique that can enable accurate estimation of changes in the subsurface properties, such as fluid saturation or reservoir depletion, by utilizing amplitude and phase information in seismic data. However, most existing 4D FWI …
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Viscoelastic full-waveform inversion: treating attenuation uncertainty, characterizing cross-talk, and quantifying confidence in inversion results
Full waveform inversion (FWI) is a powerful technique for estimating the subsurface properties which affect seismic wave propagation but it is often limited by simplistic treatment of wave propagation physics. In particular, attenuation and dispersion, which play major roles in most seismic …
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Full waveform inversion of ultrasonic phased array data for the tomographic reconstruction of heterogeneous media for NDT
… work builds upon that work by creating a full waveform inversion framework to build a tomography method that reconstructs spatially heterogeneous wave speeds maps from simulated ultrasonic phased array data. This framework consists of: a Voronoi tessellation to spatially parametrise the wave …
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Investigation of Source Extension Methods, the Discrepancy Algorithm, and Noise Estimation to Overcome Cycle Skipping in Full Waveform Inversion
Full waveform inversion (FWI) is a geophysical technique used to create highly detailed mod- els of the Earth’s subsurface which can be used to explore for hydrocarbons and to predict natural hazards such as earthquakes. Seismic waves are generated from controlled sources such as vibroseis trucks …
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Theoretical and computational studies in seismic tomography
… on a range of lengthscales, with the method of waveform inversion being a promising and relatively recent development. In this work, we present new theoretical methods which may contribute to the study and solution of seismic tomography inverse problems. In particular, we set out the …
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Frequency Domain Ultrasound Waveform Tomography Breast Imaging
… of disease. Using the principles of full waveform inversion, high-resolution quantitative sound speed and attenuation maps of the breast can be created. In this thesis, we introduce some basic principles of imaging breast disease and the formalism of sound wave propagation. We present …
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Full wavefield inversion methods for monitoring time-lapse subsurface velocity changes
… the quantitative analysis using full wavefield inversion methods which are robust in complex geology. We developed several methodologies in both the data domain and image domain to handle different time-lapse seismic acquisitions. In the data domain, we implemented double-difference waveform …
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Modelling, Migration, and Inversion for Angle Domain Common Image Gathers
… the high accuracy requirements of migration and inversion algorithms. This thesis focuses on developing an new algorithm to integrate the modeling, migration, and inversion of ADCIGs. The modeling of ADCIGs is based on acoustic and elastic wave equations, and the results are compared with the …
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